Chiral glycerol derivatives such a 2R and 2S-glycerol 1,2-acetonides have been extensively used as building blocks for the synthesis of optically-active drugs [A. Tanaka and K. Yamashita, Agri. Biol. Chem., 44 199 (1979); W. L. Nelson et al., J. Org. Chem., 42, 1006 (1977); Y. Tsuda et al., Chem. Pharm. Bull., 29, 3593 (1981)]. For example, 1 and 2 are key intermediates for the synthesis of chiral 3-aryloxy-1,2-propanediols such as R- and S-propranolol W. L. Nelson et al., J. Org. Chem., 42, 1006 (1977)]. ##STR1##
While the (+)-2S-glycerol acetonide (1) is readily available from (2R,3S,4S,5R)-mannitol-1,2,5,6-diacetonide by the method of E. Baer, Biochem. prep., 2, 31 (1952) (lead tetraacetate oxidation followed by catalytic reduction of the intermediates glyceraldehyde-2,3-acetonide), the (-)-2R-glycerol acetonide (2) is considerably more tedious to prepare and hence is less readily available. It has been prepared from the expensive, unnatural carbohydrates such as L-mannitol and L-arabinose [E. Baer and H. O. L. Fischer, J. Am. Chem. Soc., 61, 761 (1939)] and, subsequently, was synthesized from L-galactono-1,4-lactone, [S. Morgenlie, Carbohydrate Res., 107, 137 (1982)] although neither the isolated yield nor the optical purity of the product was described. More recently, 2 was prepared from tartaric acid [A. Tanaka et al., Agric. Biol. Chem., 48, 2135 (1984); K. Fujita et al., Tet. Lett., 23, 3507 (1982)] or from L-ascorbic acid [M. E. Jung and T. J. Shaw, J. Am. Chem. Soc., 102, 6304 (1980)] using relatively long reaction sequences in moderate overall yield. Because of the serious disadvantages which characterize each of the aforementioned methods, the cost of 2 at the present time is high ($3,500/Kg, Pfanstiehl Laboratories, Waukegan, Ill.).